#include <iostream>
#include <vector>
#include <unordered_map>
using namespace std;
class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        unordered_map<int,int> map;
        for(int i = 0;i < nums.size();++i){
            auto iter = map.find(target - nums[i]);
            if(iter != map.end()){
                return {iter->second,i};
            }
            map.insert(pair<int,int>(nums[i],i));
        }
        return {};
    }
};